Near-infrared (NIR) spectroscopy is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (from about 800 nm to 2500 nm). Instrumentation for NIR spectroscopy comprises an infrared light source, a detector, and a dispersive element (e.g., a prism, a diffraction grating) to allow the intensity at different wavelengths to be recorded. Fourier transform NIR instruments using an interferometer are also used, especially for wavelengths longer than ˜1000 nm. Depending on the sample, the spectrum can be measured in either reflection or transmission. Current applications of NIR spectroscopy include medical, pharmaceutical, and food and agrochemical quality control.
In agricultural applications, NIR spectroscopy is used to measure quantitative and qualitative parameters of agricultural crop seed and/or feed—such as wheat, corn, and soybeans. NIR can be used to detect major constituents in the agricultural crop, such as protein content, moisture, oil, starch, amino acids, density, and test weight. For example, Velasco & Möllers (2002) Euphytica 123: 89-93 developed a calibration equation for determining protein content in rapeseed using NIR. Individual seed spectra from 400 to 2500 nm were obtained on an NIR instrument for individual seeds. The same seeds were then analyzed for protein content using a known combustion method. Calibration equations were developed using the obtained spectral information, the reference measurements, and modified partial least squares regression. The calibration equations were validated and the authors determined that the NIR spectroscopy-derived equations were useful in assessing variations in protein content for rapeseed varieties.
U.S. Patent Application Publication No. 2011/0089090 discloses a general process for in-line NIR analysis of grain. The reference also separates grain based on measured parameters, but there is no mention of measuring grain particle size.
U.S. Pat. No. 7,508,517 discloses a process for analyzing properties of a single seed using NIR. However, it does not discuss measuring particle size.
U.S. Pat. No. 8,401,271 discloses measuring various characteristics of seeds based on image data, but does not disclose the measurement of the average particle size of particulate products.
U.S. Pat. No. 6,646,264 discloses measuring the physical characteristics of one or more seeds, including individual seed size, using NIR-type analysis. However, it is silent on the measurement of the average particle size of ground products.
U.S. Pat. No. 5,406,084 discloses a NIR measuring process and apparatus which can measure both floury commodities and whole kernels, and other constituents of pourable foodstuff products in-line. However, this reference does not disclose the determination of particle size from a population of particles.
Current methods for NIR spectroscopy do not provide for accurate, real-time assessment of the average particle size for particulate products. Accordingly, there is a need in the food and agriculture industry for a method for determination of average particle size for particulate products.